Signaling circuit



, w. H. MARTIN SIGNALING CIRCUIT Filed Jan. 2e. 1921 Patente-tl Get. 23,1923.

miran' sraras WILLIAM H. MARTI-N, F YORK, N.

'PATENT Gif-rica. f

AND TELEeaAPH comialvv, Ay CORPORATION for NEW v oax.

Appiicationnied January 2e, 1921. serial No.dizionari To all whom t mayconcern.'

Be it known that I, WILLIAM H. MARTIN, rr-rsidin,g at New York, in thecounty of Bronx and State of New York, `have in- 5 vented certainImprovements in Signaling Circuits, of which Athe following V,is a`specilication.

This invention relates to circuit arrange-V ments for signaling systemswherein signals may be either transmitted from oi received In its :morespecific" referred to, .telephone substations of thel Campbell vtypecomprise a ltransmitter receiver, auxiliary ,resistance ,and a :transfor-mer havingfa plurality of windings, and these elements, incombination with a tele-IV phone line, are so designed that: (l) thetransmitter and receiver are conjugate, that is, there is negligibleside tone in itlie receiver in Vconsequence of the actuation of thetransmitter by sou-nd waves; (2) the line and auxiliary resistance areconjugate, in Order that none of the .energy .absorbed by the substationfrom the line shall be wasted in said auxiliary resistance; (3) for agiven line havinga definite impedance,

telephonie energy deliveredv by the trans-y mitter is a maximum.; (4)the amount of energy delivered bythe line to the sub.- station is amaximum-in .other words, the impedance of the substation as seen fromthe line is equal to the impedance vof the line; (5) at a smallsacrifice of efficiency, it is possible to discriminate effectivelyagainst disturbing line noise, vas distinguished from no 4the telephoniesignals from the communicatingstation. y 1 t In common batte Aytelephone exchanges, special conditions-often arisein .which it is`desirable to connect to the switchboard subscribers who are further-away from lthe oflice than can `be reached Wit'hthe -gaugesv vY,Assiciiiioli 'ro 11i-iviiiiiioaiv` TELEPHONE of cable usually employedfor substation j loops, Without exceeding the standard 0f Y itransmission maintained for sucheXc'h-anges.

In such cases, in yorder to reduce the Atransthe switchboard, it isdesirable that Vlocal battery sets be installed, so that 'these sta;-

tions employ local battery for talking and common batteryyforsignalling. It is also desirable that, if local 'battery sets are to beemployed, high Veiiiciency ,transmitters and receivers should be used,since the use Y' of these instruments in a v-local battery set would notonly 'give a gain :in transmitting efficiency but in receivingefficiency. -'-If, therefore, a set lbe employed, A'using ya yhigheiiiciency transmitter and a receiver of the well-known electromagnet4or direct current. type, the circuit will noton'ly havethe -advantagesjust-stated, but it will also be an I improvement Afrom `afmainftenan'ce stand point, since the local battery set used onextraordinarily long com-mon lbattery vlines will then Aemploythe same:transmitter and receiver which :are ,usedinlthe ordinary com-- monbattery sets.

It is, therefore, one Lof itlie ,objects iof this .invention to -producea substation circuit having the characteristics of :the Campbell typeAand which is lso arranged that 1ra local battery may be employed fto Yenergize :both

.the transmitter and `receive-r, said localbattery being adapted to.energize these instru-`A ',ments either alone or in conjunction withcommon battery energy l supplied from' fa central vstation, :commonbattery vbeing falso yemployed for `Vpurposes of :signaling :and

supervision. l Y

Other and further objects -of the `invention will' be clear -from thefollowing vdeSC/lpf' tion, when read in connectionV with the,accompanying drawing, Kligure l of which is a schematic diagram fof thegeneral type of Campbell substation circuit from which the circuit zofthe present invention isderived; v Fig.2 of whichfis-fasimilar diagramof :the circuit `of -thepresentinventiong Fig; 3 Cofk ,f

which is -a diagram kshowing thel'substation circuit, of the gpresentfinvention in more.; detail,` uand Figs. 4 and r5 Mof.,whi ch,are

diagrams illustrating 'the Lflow ofalterfnatmittiiig and receiving,respectively.

ying.cuivre nt.duringfthe operations of transi-io n y 60 I mission lossbetween the substations land neous flow 'of alternating current.

type to which the present invention belongs, is fully set forth in theabove mentioned patents to George A. Campbell, so that it unnecessary topresent any theoretical considerations in the present instance, a simpledescription of the circuit arrangement being sutlicient fora fullunderstanding of the invention.

Referring to Figs..2 and 3, L designates a transmission line terminatingin a telephone substation arrangement comprising a transmitter T,areceiver R, an auxiliary resistance X and a transformer comprisingwindings N1, N2 and N3. Cnc side of the lineL and one terminal of thereceiver R and the auxiliary resistance X are joined together at acommon point l. The winding N2 is joined between the other terminal ofthe line L and the other terminal of the receiver R, the windings ll,and N3 being connected in series between the terminals 3 and e of thereceiver R and auxiliary resistance X. The transmitter T is connectedbetween the common point 5 of the windings N, and N3 and the terminal 3of the winding N2 so as to be in shunt with the winding Nif A localbattery B is inserted in series with the winding N1 for supplying thetransmitter current. This battery would also supply an energizingcurrent for the electromagnet receiver R through the windings N1, N3 andthrough the auxiliary resistance X. The resistance of this circuit,however, is quite high and, in order to provide a path of low resistancefor the battery supply of the electromagnet receiver B, an impedancecoil P is connected between the right-hand terminal of the battery B andthe terminal l. The impedance coil P is of low resistance so that alarge current supply is furnished to the electro-magnet receiver R, butthe inductance of the coil P is very high so that, as far'as the flow ofalternating current in the substation circuit is concerned, the paththrough the impedance coil is practically an open circuit. riheVresistance coil P is so proportioned as to supply optimum direct currentto the electromagnet receiver R. Y

The operation of the circuit when transmitting will be as indicated inFig. 4, in which the arrows-designate the instanta- The diagram of Fig.4 is simplified by omitting the direct current apparatus andillustrating only the circuits for the flow of alternating Y current.When the transmitter VT is actuated, its operation is equivalenttosetting up an alternating electro-motive force in the circuit of thetransmitter T, so that a current l, will flow at a given instant in Ythe direction indicated by the arrow to the right of the transmitter T.As the trans-` mitter T and the receiver R are conjugate, no currentflows through the receiver R in response to the actuation ofthetransmitter T and, therefore, the current L, which liows ov r the lineL, in response to the actuation of the transmitter T, must be equal tothe current T3 flowing through the auxiliary resistance X. Consequentlya current equal to the difference between the transmitter current T1,and the line current or its equivalent the current l, through theauxiliary resistance X, appears in the winding N, so that a current -Tliiows in the direction indicated by the arrow just below the windn ingN1.

The operation during reception of signals is indicated in Fig. 5. Analternating electromotive force applied to the line L, causes the linecurrent l, to flow through the winding of the coil N2 in the directionindicated. As the auxiliary resistance X is conjugate with respect tothe line L under these conditions, no current flows through the saidauxiliary resistance and, con

sequently, no current iiows through the winding N3. Tt follows,therefore, that the transmitter T is in eiiect in a local circuit withthe winding Ni, and the current l, flowing through the receiver R willbe equal to the line current L, The induced current in the transmittercircuit will flow through the transmitter and the winding N, in thedirection indicated.

The circuit above described is a development of the Campbell type ofsubstation disclosed in Fig. l of Campbell Patent 1,254,472, abovereferred to. This type of circuit is indicated schematically in F ig. land in the operation of a circuit of the type shown, in order that itmay operate as an anti-side tone circuit, 'it is necessary that in allcases the voltages between the terminals 2-3 and 3 4: be series-aidingand of the relative magnitude y, where Q' is the energy distributionratio and may be defined as the ratio ofthe energy in the transmitter tothe energy in the receiver on receiving.

The design formulae for the type of circuit of Fig.V l as given in theCampbell patent just referredl to ar as follows: limi /Bi i' N1 *l* R11+@ n=+jng 1: f ,N1 C R1` yu'ly) l l EWR@ U l R2=m R The circuit of thepresent invention may beobtained from the general type circuit disclosedi-n Fig. l by eliminating the winding N, of Fig.y l and bridging thetransmitter T across the terminal 3 and some point 5 of the l betweenthe terminals 3 and' is replaced bythe winding Ni. The windings .N1A:and

N2 in Fig. 2 correspond respectively to wind-l ings N1 and N 2 ofthecircuit of Fig. l and the number of turns effectivelyin series `beltween the terminals 3 and 4. represent the.

winding N3 of Fig. l. lThese turns and the turns of the Winding N2 ofFig. 2 are always series-aiding as above pointed out.

In general there yare `a number of possible values of N3 in Fig. 2,depending lupon sev@ eral possible arrangements of the windings on thecore. For example, if all the windings are series-aiding, then the turns`of Winding N3 of Fig. 2 will-have a value equal tothe turnsof windingN3 of Fig. l minus the turns of winding N1 of said figure. If thewindings are so arranged that windings .N2

and .N3 of Fig. 2 are aiding and winding N1 is opposing, then theturnsof Vwinding N3 of Fig. 2 will be equal 'to the sum of the turns ofwindings N3 and Nl of Fig. l. If windings N1 and N2 of Fig. 2 are aidingand N3 is opposing then the turns of winding N3 of Fig. 2 -will be equalto the turns of N1 of Fig. l

"l minus the turns of N3 of Fig. 1. y

In practice, when the transmitterfis of lowA resistance, the rsto'f-these arrangements is preferableras it requires a minimum number ofturns on the transformer.` For this arrangement, the design formulaelmay be readily obtained from design formulae (l), by considering therelation between "the unitsof Fig. l and Fig. 2 as vjust given. Thesedesign `formulae will be as follows: 3

In equations (l) and V(2) itwill be :under-` "the resistance oftheauXilia-rylcircuit and R3 the lresistance of the line,- while y is`the energy ratio previously defined. It is fapparent fromA theseformulae that VhavingV given the jline resistance and the-.resistance'of the transmitter :it is desired :to use, theV resistance: of theIreceiver and 'auxiliary-l ele.- ment, as well as the :number oftu-rnsofthe winding Aof thejtransformer, may readilybe obtained by assigningany desired Avalue y'to the ratio y; Ars pointed .out -inf.the'-Campbellpatent, adesirable value of .y is in the neighborhood oli-11.4. It willof course be obvious i thatwhile the auxiliary'elementX is illus- Vtrated :as a v.separate resistance element, :in `practice vtheresistance represented by .this

element may be obtained by ,properly design-v ing the windin N3- of Fig.-3 so that the ele-4 ments N3 and y-fmay be merged.

VIt willbe apparent that the generalprini ciples herein disclosed may beembodied in many other organizations widely different fromthose-illustrated, without departing from the invention, as defined -inthe followingclainis:v 3' .f l

What is claimed is:

l. In a signaling system, a transmission circuit, a transmittingcircuit, a receiving circuit, va balancing circuit, and a tra-nsformerhaving three windings, one `of said windings lbeing included in saidtransmis'- sion circuit, :another of said windings being included insaid balancing circuit, and the third winding being included vbetweensaid transmission and balancing circuits; a terminal vof each of `saidtransmission, receiving, and^balancing circuits being joined together,the other terminal of Vsaid receivin circuit being connected betweensaid third winding and the-circuit Vincluding one 4of the other twowindings; said transmit- .ting circuit being connected 4in shun-twithwindings being -included -in said transmis-v sion circuit, ano-ther ofvsaid windings being included 'in said `balanci-ng circuit, and the thirdwinding being included 'between said :transmission and .balancingcircuits; a terminal ofea'chfof said utransmissiomrei ceiving, andbalancing circuits lbeing joined -ftogethen the other terminal vof saidreceiving .circuit being connected 'between'.said

Vthird windingland the circuit including one i of the other twowindings; said transmitting circuit being vconnected in shunt vwith saidthird winding; Vafsource `of Vdirect current included v-inseries-withsaid third ,wind-l Ling, and a circuit having ilarge impedance :and low4resistancefdirectly lconnectedto one terminal :of said sourceand toatterminal of said :receivingcircuit.,l L

3. In af-signaling system, v4a circuit, `a' transmitting fcircuit,'za.receiving circuit, 'a balancing-"circuit, 'andra trans'- former :havinglthree fwin'diiigs, one* Lof said windings being included insaid-'transmis' transmission sion circuit, another of said windingsbeing included in said balancing circuit, and the` circuit, a balancingcircuit, and a transthird winding being included between saidtransmission and balancingl circuits; a

Vterminal oit-'each of said transmission, re-

ceiving, and-balancing circuits being joined together, the otherterminal of said receiving-,circuit being connected between said third`winding and the circuit including one fof the other two windings; saidtransmitting circuit being connected in shunt with said third winding; asource ot direct current so connected as to supply current to both saidtransmitting and said receiving circuits, and a circuit yof highimpedance but low resistance directly connected to one terminal ot saidsource and to the terminal of said receiving circuit which is joined tosaid transmission and balancing circuits.

4;. In a signaling system, a transmission circuit, a transmittingcircuit,.a receiving circuit, a balancing circuit, and a transformerhaving three windings, one of said windings being included in saidtransmission circuit, another oi said windings being included in saidbalancing circuit, and the third winding being included between saidtransmission and balancing circuits; a terminal of each of saidtransmission, re-

ceiving, and balancing circuits being joined together, the otherterminal ot' said receiving circuit being connected between said thirdwinding and the circuit including one of the other two windings; saidtransmitting circuit being connected in shunt with said third winding; asource of direct current included in series with said third winding, anda circuit of high Vimpedance but low resistance directly connected toone terminal of said source and to the terminal of said receivingcircuit whichY is joined to said transmission and balancing circuits.

5.'ln a signaling system a transmission circuit, a transmitting circuit,a receiving circuit, a balancing circuit, and a trans-v former havingthree windings, one of said windings being included in said transmissioncircuit, another of said windings being` included in said balancingcircuit, and the third winding' being included between said transmissionand balancing circuits; a terminal of each of said transmission, re-

Y ceiving, and balancingcircuits being joined sistance directlyconnected vto one-terminal of said source and to a terminal yof saidreceiving circuit.`

6. ln a signaling systema vtransmission circuit, a transmitting circuit,a receiving former having three windings, one of said windings beingincluded in said transmission circuit, another of said windings beingincluded in said balancing circuit, and the third winding being includedbetween said transmission' and balancing circuits; a terminal of eachoit' said transmission, receiving, and balancing circuits being joinedtogether, the other terminal of said receiving circuit being connectedto the junction point between said third winding and said transmissioncircuit; said transmitting circuit being connected in shunt with saidthird winding; a source of direct current included in series with saidthird winding, and a circuit having large impedance and low resistancedirectly connected to 'one terminal of said source and to a terminal ofsaid receiving circuit.

7. ln a signaling system a transmission circuit, a transmitting circuit,a receiving circuit, al balancing circuit, and a transformer havingthree windings, one of said windings being included in, saidtransmission circuit, another of said windings being included in saidbalancing circuit, and the third winding being included between saidtransmission and balancing circuits; a terminal of each of saidtransmission, receiving, and balancing circuits being joined together,the other terminal of said receiving circuit being connected to thejunction point between said third winding and said transmission circuit;said transmitting circuit being connected in shunt with said thirdwinding; a source of direct current so connected as to supply current toboth said transmitting and receiving circuits, and a circuit of highimpedance but low resistance directly connected to one terminal of saidsource and to the terminal of said receiving circuit which is joined tosaid transmission and balancing circuits.

8. In a signaling system a transmission circuit, a transmitting circuit,a receiving circuit, a balancing circuit, and a transformer having threewindings, one of said windings being included in said transmissioncircuit, another of saidwindings being included in said balancingcircuit, and

the third winding being included between said transmission randbalancing circuits; a

terminal of each of said transmission, re-

llt)

directly connected to one terminal of said source and to the terminal ofsaid receiving circuit which is joined to said transmission andbalancing circuits. i i i 9. n a signaling system, a transmissioncircuit over which direct current supply-may be furnished from a centralstation, a transmitting circuit, a receiving circuit, a balanc ingcircuit and a transformer having three windings, one of the windingsbeing ineluded in said transmission circuit, another of said windingsbeing included in said balancing circuit and a third winding being inieluded between said transmission and balancing circuits; a terminal ofeach of said transmission, receiving, and balancing circuits beingjoined together, the other terminal of said receiving circuit beingconnected between said third winding and the Vcircuit including one ofthe other two windings; said transmitting circuit bein mitted from acentral-station over` said transmission circuit is used for commonbattery supervision and signaling, while said direct `current is usedtogether' with thelocally `Asupplied direct current for energizing thetransmitter and receiver for talking pur-` poses. Y n

In testimony whereof, I have signed my name to this specification this22nd day of January 1921.

wiLLiAM H. MARTIN.-

